I have a 2006 PT Cruiser with 94k miles. About one month ago the a/c just stop working. I have just bought a freon kit and checked to see if it’s low. The reading came up with 55 (which is normal) full. I don’t know what it could be or how else to fix this.

When I ran the check for freon the compressor turned on and off about every 3-4 seconds.

Generally we don’t recommend DIY work on the A/C other than the vacuum controls. While my suggestion would be to bring it to a A/C shop (often a radiator shop in the north part of the US), I do expect some with more personal knowledge than I will respond with some ideas that may help you DIY.